The Cybersecurity and Infrastructure Security Agency (CISA) and the National Security Agency (NSA) collaborated with international cybersecurity partners to develop a guide to help network defenders harden on-premises Exchange servers against exploitation by malicious actors.

Many organizations rely on Microsoft Exchange to perform critical communications, necessitating paramount protection from malicious actors. Reported abuse and exploitation of vulnerabilities within Exchange further demonstrates the importance of implementing security best practices.

The threat to Exchange servers remains persistent. Exchange environments are continuously targeted for compromise and should be considered under imminent threat. As certain Exchange Server versions have recently become end-of-life (EOL), environments with these versions are at a heightened risk of compromise.

The authoring agencies strongly encourage organizations to take proactive steps to mitigate risks and prevent malicious activity. Additionally, the authoring agencies recommend implementing the best practices found in the guide to significantly reduce the risk from cyber threats.